The present disclosure relates to a display device, a CMOS operational amplifier, and a driving method of the display device.
In general, in a display device such as a liquid crystal display device and an Electro-Luminescence (EL) display device, which performs a display using a plurality of pixels (liquid crystal or EL elements) which are arranged in a matrix shape, the pixels are driven as a load using an amplifier installed in an output stage of a source driver. A driving capability of such an amplifier is constant if the amplifier is a class A amplifier, and varies within a certain constant range according to the load if the amplifier is a class AB amplifier.
Here, there is a case where variation occurs in the load which is driven by the amplifier, due to an influence of a large size or the like of the liquid crystal. In a case where the amplifier is class A, if the load is larger than the driving capability of the amplifier, a problem occurs in which ringing occurs in an output of the amplifier, and if the load is smaller than the driving capability of the amplifier, a problem occurs in which the output of the amplifier is overshot. A technology to solve such problems is disclosed in Japanese Unexamined Patent Application Publication No. 11-85113.
In Japanese Unexamined Patent Application Publication No. 11-85113, an amplifier is disclosed which includes a bias variable circuit that varies a bias current flowing in a differential amplifier and an output circuit. The bias variable circuit can adjust the bias current of the differential amplifier or the bias current of an output unit of the output circuit.
As a result, regardless of a size of the load of the liquid crystal, by increasing the bias current of the output circuit, it is possible to immediately reach a target voltage. At this time, although the ringing or the overshoot occurs in an output waveform, it is possible to immediately reach the target voltage, and thus, a liquid crystal display can be normally performed.